1. Field of the Invention
The invention is directed to the field of cold shrink devices and the method of their use and more particularly to a device to expand a premolded or extruded part, retain it in its expanded condition until placed over an article at which time the device is released and the part as it returns to its original size ejects the device.
2. Description of the Prior Art
Cold shrink methods are used to expand a premolded or extruded part, such as a connector or cable joint, elbow or extruded sleeve, to a size which permits it to be placed over its mating surface (eg. a prepared power cable end) without interference. The device used to expand the product is then removed by the user, allowing the premolded or extruded part to recover substantially to its original dimensions.
One well-known device is that shown in U.S. Pat. No. 3,515,798 issued Jun. 2, 1970, used a removable core to support an elastic cover in its expanded state. The core was removed to permit the elastic cover to regain substantially its original dimensions. Because of the hoop forces exerted upon the core by the elastic cover, it was often difficult, to remove the entire core. If the core's continuous strip broke at any point, it was difficult, if not impossible, to retrieve the strip and continue to remove the core so that the cover could fully recover.
U.S. Pat. No. 3,824,331 issued Jul. 16, 1974, shows a resilient tubular cover being supported in or stretched condition by a removable one piece support member positioned around the outside of the cover. Once the stretched cover is placed over the joint, for example, the inner support member is first removed and then the cover allowed to recover, after which the outer support member can be removed if desired. Any irregularities in the cable or a distorted cable contour can prevent the inner support member being removed and render the device useless.
In U.S. Pat. No. 4,267,628 issued May 19, 1981, an insulator assembly is placed in a device and the air between the walls of the insulator and the device is removed so that the assembly expands into intimate contact with the interior walls of the device. Once in place air is admitted between the insulator and device to permit the stretched insulator assembly to substantially return to its initial dimensions. The procedure is limited to thin wall insulators and can not operate upon the premolded or extruded products used in high voltage systems.
Hamel, U.S. Pat. No. 1,669,053, issued May 8, 1928, shows a cone-shaped rubber sleeve expansion member pushed along rods to expand a rubber sleeve which is placed over a club handle. The grip end is used to push expansion member along the rods to expand the sleeve and then allow the sleeve to remain on the club handle or grip after the expansion member and rods are removed. The method is used at the point of application and has a limited ability to expand the rubber sleeve and would not work with thick rubber sleeves
Dines, U.S. Pat. No. 3,946,400 issued Mar. 20, 1976, shows a sleeve expander 10 made of an outermost annulus 22, an intermediate annulus 24 and innermost annulus 26 all joined by support rods or ribs 28. The expanded sleeve (how it is expanded is not disclosed) is placed over a cable 16 and splice 14 which extends through the annuli. The to collapse the sleeve 12, the activating means 34 is pulled causing innermost annulus 26 to move to the right until it engages intermediate annulus 24 and both are pulled to annulus 22 and the three are removed. The ribs 28 remain in place between the sleeve 12, the cable 16 and the splice 14. The annuli are made in two parts so they can be removed from cable 16 when outside the sleeve 12. For short coverings two annuli can be used or their number increased for longer coverings. The presence of the ribs 28 within the completed joint can cause undesired electrical or mechanical problems.